To copy over your data you will need to open up your SQLite database (\plugins\PreciousStones\PreciousStones.db) using a tool like SQLiteManager and extract the data from it into a .sql file, clean it up so it can be the same format as MySQL, and then import it into your MySQL database.

Here's how to do that: http://www.maxkpage.com/blog/free-sqlite-to-mysql-converter-super-easy/